Control mechanism for helicopters having coaxial counterrotating rotors



Sept. 23, 1947. N, B, WALES, JR

' v ATTORNEYS Sept. 23, 1947. N, B WALES, JR v 2,427,936

CONTROL MECHANLSMFOR HELICOPTERS HAVING CO-AXIAL COUNTER-ROTATING ROTORS Filed Sept. 18, 1945 4 Sheets-Sheet 2 Ti E1.

i Clockwise P01-or? olf/vm? CLoc/rw/SE /Porop k Pw/w1, bm, J

y ATTORNEYS Sept. 23, 1947. N B WALES, JRA 2,427,936

CONTROL MECHANISM FOR HELIGOPTERS HAVING CO-AXIAL COUNTER-ROTATING ROTORS Filed Sept. 18, 1945 4 Sheets-Sheet 3 NET CANCELLATION 0F LIFT CHANGE UPPER K070i? DECREASED L/FT INcEEAEo L/FT I UPPE'RAYJTOR` DEcREAsED L/FT Il Il ,wwe/e Parole NET I' l l NET I x- DEcEEAsED l I [NCEE-Asso -X L/FT /FT y RESULT-ANT COUPLE f DECPEAED L/FT I INVENTOR NA THAN/EL B. WALES JP.

ATTORNEYS Sept. 23, 1947. N. E. WALES, JR 2,427,935

" CONTROL MECHANISM FOR HELICOPTERS HAVING V CO-AXIAL COUNTER-ROTATING ROTORS Fild Sept: 18,. 1945 4 Sheets-Sheet 4 Tg5. i 7 T1?? LATER/:L ANG'LESELEcT/ON i l I /ISCEND DESCgND CONTRO/ #RE VERSE PEDAL INVENTOR NATHAN/EL B. WALES J1?.

ATTORNEYS eeltieefheve been tcounter-rotating rotorsl Patented Sept. 23, 1947 HAVING COAXI'AL lnofrojns CONTROL MECHANISM-FOR HELICPTERS correntemente Nathaniel.: iB-iWe'le'S, Jr-f New' York, N-:Y- Applicatonseptember l18, 1941"., Seial No;

f5-Claims- 1 .This .invention relates to helicopter. .aircraft of the coaxialrotor type, andtoa controlsystem and method for stabilizing and directing. such aircraft, andhas .for .itsobjectthe improvement and simplificationlofzthe Vmechanism and, controls 5 .ings,embodies this method of` phasedfhft cycles thereof.

In the/.design .of helicopters, itv has been recognized that means must be provided to compensate forthe aerodynamicreaction torque of. any` rotor,

or rotating airfoil, and also that means lmust -be Vproyidedefectivjelyto inclinethe lift Avector to Ythe liftingprotororrotors to the vertical in any chosendirection under control of the `pilots() vas to set up atranslational `force component Aof the lift vector in the horizontalvplane. g Heretofore 1 it has. been alsolrecognizedthata coaxial construction ycomprising two lifting rotors counterrotating about a common aXis, would .be a desirable and compactmeans for neutralizing the reaction torques effective on thehelicopter. However, in the prior art the control means associated ywith s\ 1 ch countererotating rotorsfor inclining their liftl vector tothe .vertical have been Y of vsuch complexitythat serious .engineering` diiiencountered in executing such en -design." Infparticutan v the method of cyclic pitch control, which hasbeen themost successffe-l. ef. SeeY-eentrel. syeftems; he-S .required .the use -efe -SWeSh .plete .tree ref.; eem meeheeiem hei/.151g

two degrees ofangularfreedom to allow the pitch of the individual rotor Vair f oilsto change cyclically withany chosen anilnlitude about any chosen index .point of their ro.tation,and in addition vhaving one Adegree of axial translational-.freedom to prmitlalteration ofthe total effectivepitch of the. rotor for vertical liftcontrol. T Ihis typeeof mechanism `with it-s three degrees of control fredom has discouragedthe use `of a coagialtype of construction .due tothe consequent complexity and weightof duplicatingthese.controls on two 'concentric rotors. For this reason, designers havebeen forced to. include an auxiliary means for counteractingthe rotorreaction torque, :such as by means afan additional propelleracting in the vhorizontal plane at va point remote from 5 the axis of the main rotor.

The present invention embraces a method tor combiningethe instantaneous lifting forces vof two coaxial counter-rotating air foils so'that full control of the inclination and magnitude ofthe resultant liftvvector is possible while u-sing only two degreesof control freedom for eachof the two This invention compri-Ses first, establishing a sinusoidal or other suit- .able variation oflfixed amplitude of the lift for;

each ofthe rotating .air foils .of the rotors sothat each rotor experiences a resultant .aerodynamic couple of iixedmagnitude ,about .an axisperpendicular to the axispf rotation, and..second,..phas

ring theaxes lof these rotor, couples so that their Cl: 2441-17) 2 resultant .produces therdesired magnitudesand -.direction-of-fcontrolcouple.. if Thus, the. adjustable e control of 'phasewomprises-the thi1`-d...degree of control'freedom. l' i The illustrative mechanism shown in thevdrawbyl means oftw`o .cam` mechanisms` capable-of fcyclically imposingfa fixed amplitude oscillation of pitch on the blades, ofmeach of-the tworotors Aas; they revolvevinopposite directions."- The phase `relationship.between wthese two cams -will-then determine the .direction'- and magnitude .of inclination to the vertical to which the entire coaxial system will be subjected. Inparticulan when'the phase of Ltheixed amplitude tilting couples offthe two rotors is adjusted so that they arel displaced from one anotlnerv by V1 80,-there will be no resultant tiltingcouple and the helicopter will-'remairin vertical equilibrium. On the other` l 1and,if thef-phaseofthetwo cams does `not bringthe duad'rantof maximumlift for-' one rotor into coincidence'withthe quadrant` of minimum -lift Af'orthe, other rotor, as in the condition for vertical edui1ihri1m,then there will be a reeelen re1'e2ie;.i`e *iheerffjaeie' .Willjdepeldlen the phase ofthe two cams relative to this; air- :.f..11ene .T11e .PheSe.eftheee Xed-eenieureems een. be. ednetedt retetineitheeems vaterflue .teeeeeeleeetriew .e theieeeiiel weer exiefthus leeiding @repleteletereleoetrel.by ene degree offreedomperroton The total effective lift for eeeh .retermey beeeetrelled been exieljmovemeet eftheeemeriue tubesrandtsothe entire rotoranis. u

Although the.; 'illustrated mechanism fer embed-ying ely' eenirerlrelies the .lise lef Piteh Vchange in order tn intrgduce theiixed Aamplitude -1ft variation required bythis meth'od, it is evidentthatthe sameinethod could e r' r11 3l oy a cyclic variation in area, 'l shape, velocityor any other characteristic-of `the rotating air"v foilwhich rnay A contributerto itsliftg without 'departing from :the-scope of the invention Similarly, V' 'although a cam; mechanism isll depicted asthe meansfor `changing the phase. of-ffthese-iixed amplitude lift variations, any other. 'suitable 'rnean`s familiar tothose skilled immearemay be use@ tqacmeye .this function.

The nature oil-.myncontrolesystem.is such' .that zthetfourdegrees.. ofi-.freedom used tol controlI the maneuverscffthe helicopter`;lhamely, one degree of translationaltfeedom..an'dione-dgree otro.-

Specifically, the four resultantl control operations which result from these two classes of displacement for rotation and translation, and the consequent behaviour of the helicopter are as follows:

(a) Common translation of the cams results in control of the ascent or descent. K

(b) Relative translation of the cams results in control of the rotation or steering of the helicopter about its vertical axis.

(c) Common rotation of the cams results in selection of the direction in a horizontal plane along which a phase diierence between them will produce translational forces Von the helicopter.

(d) Relative rotation of the cams from the neutral 180 position results in the production of a couple which will cause the helicopter to move in the direction chosen by c.

Consequently, it is an integral feature of my invention that anaircraft control system closely analogous to the control operations of a conventional automobile may be adopted in which selection of the direction of motion is made in one operation, as by the steering wheel of an automobile, while the execution of this motion in the direction selected by the wheel is made in an independent operation such as by operation of the accelerator (or clutch) of an automobile.

Thus, in the Vcontrol system of my invention it is made possible t provide a control column whose motion selects the direction of lateral motion as in operation 0" controlling the common rotation or phasing of the cams, whereasV the execution of this selection may be made by a pedal (analogous to an automobile accelerator) which controls the relative rotation ofthe cams as in operation d above. Furthermore, since the sense, or vectorial sign, of the couple produced by operation d depends on th'e sense of relative rotation between the cams, it is possible to provide a second pedal (analogous to the brake of a .conventional automobile) which will perform operation din reverse, thus braking the motion in the selected direction, and if continued, will produce motion in reverse of the selected direction.

`This allocation of control, which functions so that selection and vexecution of horizontal motion are distinct operations, is a novel contribution to the art of aircraft control which minimizes the skill and training required of the operator, since h'e may apply to night the natural coordination reexes acquired in automotive control.

An additional feature of this invention lies in the relation of the cyclic pitch changes of the rotors to the direction of lateral motion consequent from the phasing of the two pitch control cams. It will be seen that the'necessary conditionfor tilting to produce translational motion of the helicopter is also one in which the blades are feathered for lesser pitch when moving in the direction of the helicopter (that is, into the slipstream) and for greater pitch when moving opposite the motion of the helicopter (with the slipstream). This action tends to minimize the drag and turbulation consequent to ,excessive slipstream velocities over thev air foils, `and thereby improves the limiting ,speed and performance which th'e helicopter will exhibit.

4 A better understanding of the invention may' be had by referring to the drawings wherein:

Fig. 1 is a side view in elevation of a helicopter aircraft embodying my invention, and showing in broken line the relation of interior components of the system;

tional motion along the horizontal line XX;

Fig. 6 is a transverse verticalsection through the control unit showing the control column and wheel;

Fig. l is a vertical section along line 'I-I of Fig. 6 and Fig. 8 is a horizontal section along line 8 8 of Fig. 7.

Referring to Figures 1 and 2, the airioil rotor blades I and 2 may be seen to be journalled in hub member 8, thus comprising the upper rotor, which is driven in the clockwise direction as seen from above. Similarly, the blades 3 and 4 are journalled in hub II6 to form the lower rotor, which rotates in the counter-clockwise direction. The cam arms 9 and I0 are integrally secured to rotor blades I and 2 respectively, and both arms engage the groove I'I in the relatively stationary cam cylinder 5. Consequently, on rotation of the rotor, the blades I and 2 are caused to undergo a cyclic pitch change of fixed amplitude, as determined by the closed cam track I1. In like manner, the lower rotor blades 3 and 4 with integral cam arms II and I2 are made to follow the pitch cycle imposed by cam track I8 in cam cylinder 6. The coaxial rotor assembly together with their concentric control cam tubes are journalled in the supporting casing 24 which extends downward within the helicopter body IIO to form the drive and control mechanism housing. Power from -motor |04 is delivered through transmission I 0'I to the rotors by the drive mechanism in casing 24. Airscoops |09 and radiator I 06, together with appropriate conduits, form the principal components of the cooling system. The landing and road gear comprise the two steerable front wheels I 0I and I02 together with the single rear drive 'Wheel |63. Power transmission means in unit |07 are provided to supply power through auxiliary road transmisison I08 via torquetube I05 to the rear drive wheel |03, thus making the vehicle capable of either road or air navigation.

The transparent nose section |00 is hinged about an axis near the upper joint between it and the body I I0, thereby affording direct access to the seat I I I which accommodates both pilot and passengers. 0n a level below the feet of the pilot, casing 'IQ-86 houses the control transmission system. Control column 56 with the integral steering wheel 52, is journalled within casing 'IS-30. The control motion of the control column 56 and wheel 52 together with Ythose of pedals 89 and 99 are coordinated in the control transmission unit liland transmitted by four chain drives via suitable idler guides-(not shown) to the cam control mechanism in casing 24.

v- Figures 3 and 3a show the rotor cam system cam 6 relative to the airframe.

and drive mechanism in detail. In Figure 3, power from the drive motor and transmission is delivered through shaft 35 journalled in bearing 34 secured to casing 24, to bevel gear 33 where it is distributed between the reduction bevels 21 and 39. This arrangment causes gears 21 and 30 to rotate in opposite directions, Power deliv ered to gear 21 is transmitted via integral torque tube 2l and hub IIE to the rotor blades 3 and 4, whereas power delivered to gear 39 is transmitted via integral torque tube 20 and hub 8 to the rotor blades I and 2. The lift thrust and radial loads imposed on torque tubes 20 and 2l are absorbed by the bearings 3l and 28 respectively which in turn are secured to the frame casing members 32 and 29 respectively. Each rotor blade is journalled into its hub by means of the bearing stacks 'I which are combination radial and thrust bearings as shown in further detail in Figure 3a. The blade is retained against centrifugal displacement by shoulder studs 26 which are secured to the blades and abut against the bearing stacks 1. The bearings 1 are retained in their respective hubs by bushings 25.

Although it is not an essential part of my invention that the cycle of lift variation be sinusoidal, in the preferred embodiment shown in Figure 3 utilizing pitch variation, the cam groove I'I cut into the periphery of cam member 5 has a. straight line projection in the plane passing through the axis of cam cylinder 5 and perpendicular to the plane of Figure 3. Thus the motion which it imparts to the spheroidal hardened cam follower I4 which engages this groove is substantially sinusoidal. This motion is transmitted through cam arm I6 to blade 2 so as to impose on it the required cyclic oscillation of pitch. The lever arm through which this cam action operates may be seen clearly in Figure 2. In the position shown, blade 2 is moving away from'the observer in Figure 3, and consequently the upward displacement of I6 results in a decreased pitch for blade 2. On the other hand, blade I is in a position of increased pitch since its cam arm 9 is engaging the cam groove I1 at a position180 displaced from arm I6. Similar reasoning would apply if three or more blades were used instead of the two illustrated. y Conversely, the cam groove I8 in cam cylinder 6 is geometrically identical to groove Il, but is so positioned that in the position shown the counter-rotating blades 3 and 4 occupy positions of increased and decreased pitch respectively by virtue of the cam arms |I and I2 with the respective cam followers vI5 and I6.

Cam cylinders 5 and 6 are secured to control tubes I9 and 22 respectively. Thus rotation of these tubes together will change the direction for which a, given phaserelation obtains, whereas relative rotation of these tubes with respect to each other will change the phase relations of the cams for a given direction. The mechanism for controlling these phase relations is shown in the lower casing 24 to which the entire coaxial assembly of torque tubes I9, 28, 2l and 22 is jour- .nalled by bearing 23. Bushing 45, which is secured to cam tube 22, is splined to sprocket 48 so that linear movementof chain 49 which engages this sprocket will control the absolute phase of Similarly, linear motion of chain 4l engaging sprocket 46 splined to bushing 31 secured to tube I9 will control the absolute phase of cam 5 relative to the airframe.

and by studs I I2 engaging groove H3 respectively.

For control of ascent or descent of the heli copter, and also for steering purposes, it is further necessary to control the total pitch of each rotor. This total pitch may be considered to be the average pitch of a rotor blade through its cycle of pitch variation. The means shown to effect this control comprise the gear segment 46 engaging the cylindrical rack member 44. Since rack Imember 44 and integral bushing 45 are secured to the cam tube 22, rotation of gear segment 46 by sprocket 50 through shaft 41 by linear movement of chain 5I, will cause the entire cam member 6 to rise or fall relative to the plane of the rotor blades 3 and 4. Similarly linear movement of chain 43 will control the increase or decrease of the total pitch of the upper rotor` through the elements 42, 39, 38, 36, I9 and 5 respectively. The cylindrical form of racks 44 and 36 allows free rotation of the cam tubes independently of any translation, whereas the splined bushings 45 and 31 allow free translation of the control tubes independently of any rotation.

Referring to Figures 6, 7 and 8 which illustrate the control unit, the mechanism may be seen y which translates the motions of the controls into ,The axial displacement of sprockets 46 and 48 l is prevented by vstuds H4 engaging groove H5,

the appropriate linear displacements of the control chains 5 I, 49, 43, and 4 I. The control column 56 is secured at the top to the steering wheel bearing member 55, and at the bottom to fitting 58 which in turn is pinned to shaft 59. Shaft 59 is journalled in the gimbal frame 64, thus allowing the control column to be moved from left to right as seen by the pilot, about the longitudinal axis 59. Gimbal frame 64 is itself journalled by supports 83 which are integral with the lower casing 86. This gimbal support allows the control column to be moved fore and aft in rotation about the transverse axis of bearings 83. Thus column 64 is effectively pivoted at or near its base t0 move in four directions, Steering wheel 52 is secured to shaft 53 to which is pinned sprocket 54, the entire assembly being journalled in the fitting 55. Chain 51 links sprocket 54 with sprocket 66. However, sprocket 69 which is journalled on, but not secured to shaft 59, is integral with bevel gear 63. Gear 63, in turn engages on one side the mating bevel gear 6I which drives sprocket 65 through shaft 6l, and on the other side it engages bevel gear 62 which drives sprocket 66 through shaft 68. Shafts 61 and 68 are supported concentrically within the bearing sleeves of gimbal frame 64. Consequently, rotation of wheel 52 will cause sprockets 65 and 66 to rotate in opposite directions, whereas inclination'of the control column about the bearings 83 will cause sprockets 65 and 66 to rotate in the same direction.

Movement of the control column to left or right as seen by the pilot produces rotation of shaft 59. This rotation is transmitted through universal joint 69, telescopic coupling 'I6-1I and second universal joint 12 to the shaft 13 and thence to bevel gear l5. This type of coupling allows the gimbal frame 64 to rotate about its bearings 83 without interfering with the transmission of rotation from shaft 59 to bevel gear'15. The remaining mechanism is designed to combine the control Arotation of gear 'I5 due to lateral movement of the control column, with the control rotation due to actuation of the pedals 89 and 69 in Such a way that the one will produce a differential motion of sprockets 81 and '91, whereas Vthe other will produce a common motion of these sprockets.

Shaft 16 is supported on bearing blocks 88 and 98. Pinned to this shaft are pedal 99, spring biasing arm 11, and bevel gear 92. Gear 92 is engaged by reversing idler bevel gear 99 journalled on support 9|. Bevel 9D in turn engages 'and bevel gear 8| which engages bevel gear 15,

form an integral unit floating on shaft 16. Similarly, bevel gear 82 engaging bevel gear 15 on the other side from bevel gear 8l, together with bevel gear 93 form an integral unit iloating on shaft 16. Thus a given rotation of bevel gear 15 due to lateral inclination of the control column Will produce opposite rotational displacements of bevel gears 83 and 93, whereas a given rotation of shaft 19 due to operation of pedals 89 or V99 will produce common rotational displacements of bevel gears 84 and 94. Both bevel gears 83 and 84 engage the differential bevel 85 which is journalled by a pin on arm 89. This arm and pin are integrally connected to sprocket 81 and together iioat on shaft 16 or axis. In like manner, bevel gears 93 and 94 engage the dierential bevel gear 95 carried on arm and sprocket assembly 98 and 91 freely journalled on shaft 1B. These two differential transmissions each have the property of independently and algebraically combining the angular displacements of their coaxial drive pinions. Thus a given rotation of control bevel 15 will rotate the sprockets 81 and 91 in opposite directions, whereas depression of either pedal 89 or 99 will rotate these sprockets 81 and 91 in a common direction.

However, in order to execute the'control operations listed above as operation c and operation d, it is required that inclination of the control column produce a common displacement of chains 4l and 49 and that operation of the 'pedals 89 and 99 produce a relative displacement between these chains. Consequently, in order to reconcile these reversed conditions obtaining between the convenience of the mechanical arrangement, shown in Figure 8, and the control requirements, it is simply necessary to reverse the chain 4| by a crossover in the idler arrangement (not shown) which guides the chains between the transmission case 24 and 'the control case 89. Due to this reversal, it follows that inclination of the control column will 4produce a common rotation of the phase of cams -5 and E, whose direction of rotation Will depend fon the direction of inclination. This common rotation thus selects the lateral direction in which a diierential phase shift will set up a translational couple in the helicopter. Subsequent to this selection, depression of pedal 99 Will cause a diflerential motion of cams 5 and 6 thus opening up segments of net increased and decreased lift for the two rotors. Conversely, depression of pedal 89 will set up a translational couple in the opposite direction of torque from that set up by pedal 99.

The operation of my method of phased lift cycles may be followed with reference to Figures 4 and 5. In Figure 4, the outer circle represents the cycle of lift effective during one cycle of rotation for the clockwise rotor while the inner circle represents the corresponding cycle of lift for the counter-clockwise rotor. The segments of these two circles shown as solid arrows represent that part of the cycle during which the fixed lift changing device, in this case the pitch cam 5, causes any rotor blade traversing this segment to increase its lift above the average pitch, whereas the remaining 180 segments shown as broken line arrows represent that part of the cycle during which the blades are caused to decrease their lift below the average lift throughout the cycle The point of the cycle at which thelift is increasing through the value of average lift may be considered to be the index point of reference for that rotor. In the position shown the indices for both rotors are coincident and are on the line X-X. Under these circumstances it may be seen that the region of increased lift for each rotor coincides with the region of decreased lift for the other rotor. For this reason a net cancellation of lift variation takes place and the resultant lift Vector is equal to the sum of the average lift vectors foreach rotor and lies in the vertical line, thereby giving rise to vertical equilibrium for the helicopter.

On the other hand, the corresponding diagram for the condition in which the index points for the two cycles are not coincident is shown in Figure 5. In this case it is evident that there Will be a segment in which the regions of increased lift will overlap in coincidence, and that there will be anequal and opposite segment in which the regions of decreased lift will coincide. The consequence of this condition will be experienced `as Vone region of net decreased lift and an opposite region of net increased lift. These unbalanced aerodynamic reaction forces will produce a couple about the axis Y-Y, thereby Atilting the combined average lift vector from the vertical along the direction X-X which bisects the segments of coincidence. This inclination of the total lift vector will produce a component of the lift vector lying in the horizontal plane, thereby moving the helicopter in the direction XX. Evidently, the common rotation of the index points of the two cycles relative to the airframe will change the lateral direction in Which the helicopter is propelled. If the axis X-X lies athwart the helicopter, the ship will move sidewise, whereas if it lies along the fore and aft line, the ship will move forward or reverse depending on the sense of the axis X-X relative to the airframe. At any intermediate angle of orientation for the line X-X the ship will execute a crabbing motion.

In the control of the helicopters rotation about a vertical axis, it may be seen that no rotation will obtain if the aerodynamic reaction torques for the two counter-rotating rotors are equal and opposite. This situation will occur when the average pitch of the two rotors is equal. However, if the average pitch of the two rotors is changed relative to each other by the relative translation of camsv 5 and 6 by sprockets 5l!v and 42, then their reaction torques will not cancel, and the difference between their turques will be applied to rotate the ship about the rotor axis. This operation is eil'ected by turning the steering wheel 52 in the desired direction of rotation.

The operation of the helicopter is recaptulated in the chart below which relates the cam functions as transmitted by the 'chains'SL 49,4!

ver vof the ship:

Control Movement Resultant Maneuver Cam Function Wheel turned clock- 'Ship rotates clockwise. Relative total pitch wise. change.

Wheel turned coun- Ship rotates counter- Relative total pitch terclockwise clockwise. change.

Column pulled back, Ship ascends Common total pitch v increase.

Column pushed for- Ship descends Common total pitch war decrease.

'Column inclined to Angle of motion to Common cam phasleft selected. ing.

Column inclined to Angle of motion to Common cam phasright. right selected. ing, y

.Right pedal de- Shipmoves forwardih Relative cam phaspressed. selected direction. ing.

-Leftpedal depressed. Ship moves in reverse Relative cam phasof selected motion. ing.

It is to be noted that in the manual operation which inclines the control column 55 to the left or right for selection of the angle of lateral motion it is a natural tendency of the operator to maintain his grip on the steering wheel 52, which `controls azimuthal rotation, in such a way that a given radius of the wheel remains parallel to its previous direction. Consequently the selection of the angle of lateral motion is made without introducing the change of azimuthal direction which would follow if the control column were laterally inclined without the relative rotation between bearing 55 and shaft 53 consequent lto the operators natural parallel control motion noted above.

From a safety standpoint it is also to be noted that in the event of motorfailure the ship may descend under full control of the operator, by suitable manipulation'of the controls, since the method of phased lift cycles is'equally applicable to the control of lateral stability whether the rotors are receiving rotational energy from the drive motor or from aerodynamic forces consequent to the loss of potential energy of the ship in descent.

To descend under these circumstances, the

operator gives the ship a forward translational motion by operation of pedal 99 at the moment of motor failure and while the rotors still retain their inertial kinetic energy. This forward motion will sustain the rotation of the rotor in a `manner analogous to 'the operation of an Autogiro due to the fact that the blades of the rotors lare cyclically feathered, in the preferred embodiment of my invention, so as to present a lesser pitch when moving in the direction of translation and a greater pitch when moving opposite this direction. The resultant aerodynamic couple maintains the rotation of the blades at the expense of the potential energy of the ship in descent. Consequently the ship will execute a glide angle whose attitude and direction is under full control of the operator.

What is claimed is:

l. In helicopter aircraft having coaxial contravrotating rotors `each including a plurality of airfoils, means for controlling the lateral stability of said aircraft, comprising in combination, means including cams and cam followers linked to said airfoils for generating a cyclic variation of fixed amplitude for the lift of each of said airfoils such 'that each of said rotors receives a resultant aerodynamic couple of fixed magnitude about an axis perpendicular to the axis of rotation, said cams being of fixed amplitude and movable in two degrees of freedom only, viz., longitudinally to the axis of rotation of said rotors and rotationally in a lplane'perpendicular to said axis of rotation-andmeans for rotating said cams withrespect to eachother, Whereby'to adjust the phasing of the axes ofsaid vresultant rotor couples so that their combined resultant produces the 'desired magnitude and direction-of control couple.

2. In helicopter aircraft having coaxial contrarotating rotors each'includingfa vplurality of airfoils, means 'for controlling the lateral stability of said aircraft, comprising in combination a similar fixed contour cam for each rotor mechanically linked to the airfoils in that rotor to control the cyclic pitching `of said airfoils such that cach of saidrotors receives a resultant aerodynamic coupleof :lixedmagnitude about an axis perpendicular to the axis of rotation, and means for adjusting the relative phase of said Icams vin a plane perpendicular to Vsaid 'axis of rotation so that the combination of said resultant rotor couples produces a control couple of such magnitude and direction as to :establish the components of velocity and direction of vtranslational motion in the horizontal plane ofsaid aircraft.

3. In helicopter aircraft the combination comprising two coaxial Ylifting rotor airfoils positioned in different planes, motive means for rotating said airfoils in opposite directions about an axis of rotation, means including an independent iixed contourcam .associated with each rotor causing said airfoils to undergo fixed amplitude cycles of pitch'variations, first and second control means operable vindependently of each other, said first control means "being operableto move said cams in ar first degree of rotational movement and constructed and arranged to rotate said cams selectively .in the same and opposite directions to control 'the phase of said cycles of pitch variation so as to set uparesultant aerodynamic control couple about a Vhorizontal axis tending to tilt saidaircraft, and said second .control meansbein'goperable exclusively to move said cams in a second degree of translational movement with respect `to said axis to control the average pitch of the airfoils of each of said rotors so as to set up a vertical translational force tending to produce ascentor descent of said aircraft.

4. In helicopter `aircraft having similar coaxial contra-rotating rotors Veach including a plurality of similar airfoils, a cam `for each rotor, said cams being similar and mountedc'oncentric with each other and with said rotors, lacarn follower for each airfoil, means vlinking each airfoil with its corresponding cam follower whereby the effective lift of said airfoil changes with the position of the follower on said cam, rst un-control means operativeselectively to impart Yto said cams either common or relative translational 'motion or both, and second uni-control `means operative selectively to impart to said cams either Icommon or relative rotational motion, or both, whereby the flight of thev helicopter may :be controlled in four degrees of freedom'with two 'control means.

5. In a mechanism for the control of helicopter aircraft having an airframe, the combination comprising, a first control shaft, a first cam having a linear cam trackko'f fixed inclination relative to the axis of said first control shaft, said cam being mounted on said shaft so as to be movable thereby longitudinally and rotationally with respect to said` axis, a'flrst power shaft concentric with said first control shaft, ars't rotor coupled tosaid power shaft and having a plurality of airfoils, each airfoil being rotatable on its own longitudinal axis, cam follower means individual to each airfol and mechanically coupled thereto to rotate its airfoil in accordance with its position in said cam track, asecond control shaft concentric with said first named shafts, a second cam having a linear cam track of fixed inclination relative tosaid axis, said second cam being mounted on said secondY controlshaft so as to be movable thereby longitudinally and rotationally with respect to said axis, a'second power shaft concentric with said other shafts,`a second rotor coupled to said second rotor shaft so as to rotate in the opposite direction to said first rotor, said second rotor having a plurality of airfoils each of which is rotatable on its own longitudinal axis, cam follower means individual to each of said last mentioned airfoils and mechanically coupled thereto to rotate its airfoil in accordance with its position in said second cam track, and means for selectively moving each of said cams longitudinally and rotationally from a common position in said aircraft.

6. In a mechanism for the control of helicopter aircraft having an airframe, the combination comprising, a first control shaft, a first cam having a linear cam track of fixed inclination relative to the axis of said first control shaft, said cam being mounted. on said shaft so as to be movable thereby longitudinally and rotationally with respect to said axis, a first power shaft concentric with said first control shaft, a first rotor coupled to said power shaft and having a plurality of airfoils, each airfoil being rotatable on its own longitudinal axis, cam follower means individual to each airfoil and mechanically coupled thereto to rotate its airfoil in accordance with its position in said cam track, a second control shaft concentric with said rst named shafts, a second cam having a linear cam track of fixed inclination relative to said axis and similar to said first cam track, said second cam being mounted on said second control shaft so as to be movable thereby longitudinally and rotationally with respect to said axis, a second power shaft concentric with said other shafts, a second rotor coupled to said second'rotor shaft so as to rotate in the opposite direction to said rst rotor, said second rotor having a plurality of airfoils each -of which is rotatable on its own longitudinal axis, cam follower means individual to each of said last mentioned airfoils and mechanically coupled thereto to rotate its airfoil in accordance with its position in said second cam track, means for rotating said cams in either direction around said axis, and means for moving said cams longitudinally of said axis and in respect to said airframe.

7. In a ight control mechanism for Lhelicopter aircraft having an airframe, a pair of contra-rotating rotors each including a plurality of airfoils, the combination which includes, two concentric control tubes each capable of rotation and translational movement, a fixed contour cam mechanically coupled to each tube so as to be rotated and translated thereby, a cam follower and link connecting each airfoil with its respective cam to vary the pitch of said airfoil in accordance with the position of its follower on said cam, a control column effectively pivoted to said airframe, a steering member journalled to rotate on said column, means linking said column and said control tubes responsive to the longitudinal inclination of said column about its effective pivot to effect common translation of said tubes to change the average pitch of both said airfoils thereby to control the vertical motion of said aircraft, means linking said steering member to said control tubes responsive to the rotationof said steering member to effect relative translation of said tubes to change the relative pitch of said airfoils thereby to control the rotation of said aircraft about a vertical axis, means linking said column and said control tubes responsive to the lateral inclination of said column to effect common rotation of said tubes to change the common phase of cyclic pitch of said airfoils thereby to control the selection of the direction of horizontal mo,- tion with respect to the axis of said aircraft, pedal means, and means linking said pedal means and said control tubes responsive to movement of said pedal means to effect relative rotation of said tubes to change the relative phase of cyclic pitch of said airfoils thereby to control the velocity of forward and backward motion of said aircraft in the direction selected by said means responsive to the inclination of said column.v

8. In a flight control mechanism for helicopter aircraft having an airframe, a pair of contrarotating rotors each including a plurality of airfoils, the combination which includes, two concentric control tubes each capable of rotation and translational movement, a 'fixed contour cam mechanically coupled to each tube-so as to be rotated and translated thereby, a cam follower and link connecting each airfcil with its respective cam to vary the pitch of said airfoil in accordance with the position of its follower on said cam, a control columneifectively pivoted to said airframe, a steering member journalled to rotate on said column, to control the rotation of said aircraft about aV vertical axis, control means linked to said control tubes to effect common translation of said tubes to change the average pitch of both said airfoils thereby to control the vertical motion of said aircraft, means linking said column and said control tubes responsive to the lateral inclination of said column to elfect common rotation of said tubes to change the common phase of cyclic pitching of said airfoils thereby to control the selection of the direction of horizontal motion with respect to the axis of said aircraft, pedal means, and means linking said pedal vmeans and said control tubesresponsive to movement of said pedal means to effect relative rotation ofsaid tubes to change the relative phase of cyclic pitching of said airfoils thereby to control the velocity of forward and backward motion of said `aircraft in the direction selected by said control means.

NATHANEL B. WALES, JR.

. REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Date 

